This study seeks to identify alterations in immune cell function due to exposure to organophosphate compounds. These compounds, as a class, are used extensively in agricultural (pesticides, fungicides), industrial (plasticizers, additives, recovery agents), and in day-to-day applications (lawn and garden products, lubricants, varnishes). Previous studies have clearly demonstrated the neurotoxic action of these compounds; safe exposure levels based on these data have been determined. However, recent information suggests effects on cells of the immune system to occur at levels significantly lower than those required for neurotoxicity. The present study focuses on the effects of triphenyl phosphate, a 'model' organophosphate, on cells of the monocyte/macrophage lineage. These cells are essential to the induction and regulation of immune reactivity; they also play a crucial effector role in immune responses and are important in normal development and repair processes. Evidence from in vivo and in vitro studies suggests the monocyte/macrophage cell lineage to be sensitive to organophosphate compounds. The proposed studies, using control and treated murine and human primary cell cultures and cell lines, investigate three specific areas where preliminary work has shown macrophage function to be altered by TPP and similar compounds. These include: (1) Alteration in parameters critical to antigen presentation and cell-to-cell cooperation. Surface antigen expression will be determined by fluorescence activated cell sorting (FACS), light and electron microscopic immunocytochemistry, and ELISA. Correlative IL-1, phagocytosis and antigen presentation assays will be performed. (2) Effects of TPP on esterase enzyme activity in mature cells and cells at different stages in the differentiation pathway. Light and fluorescence microscopy and FACS analysis of esterase activity will be done. Correlative FACS analysis of esterase activity, surface antigen expression, and cell size and complexity will be performed. Recently developed procedures for simultaneous observation of surface antigens and esterase activity will be employed, as will studies on the effects of TPP on extracted esterase isoenzymes. (3) Alteration in precursor cell differentiation and gene expression due to TPP exposure. Precursor cell fines, which can be induced to differentiate to mature monocyte/macrophage-like cells, will be examined for differentiation-specific markers (e.g., morphologic changes, nuclear morphology, DNA synthesis, rate of division, cell size, presence of characteristic differentiation/maturation antigens, presence of surface enzymes, and activation of certain oncogenes), both in the presence and absence of TPP.